Information provided by parents about their children's dietary intake and/or physical activity (PA) often is inaccurate because children eat meals and are physically active in locations at which parents are not present (e.g., at school). Numerous studies rely on children to self-report dietary or PA information. We know of only one validation study in which children simultaneously recalled both, but no recalls were obtained of diet only or PA only. An integrated recall of diet and PA should enhance accuracy by facilitating correct episodic memories rather than semantic (general) memory. Errors in reports of diet and PA can be identified in validation studies in which self-reported information is compared to reference information from a method independent of the subject's memory. For validation studies, observation of children eating school meals and measurement of PA using accelerometry provide reference information about children's dietary intake and PA at school, respectively. Aim 1 is to develop, pilot-test, and validate an interview protocol to obtain from children an integrated recall of dietary intake and PA that occur at school. Aim 2 is to determine the influence of grade and retention interval on the validity of our interview protocols for diet and/or PA. The target period (about which information is to be reported) and interview time (when the interview is conducted) may vary for any given interview. Target period and interview time define the retention interval (elapsed time between when the event[s] happen[s] and the interview), which influences recall accuracy because in general, as the retention interval increases, accuracy declines. An exploratory aim is to assess relationships of body mass index (BMI) and social desirability with the validity of our interview protocols. Data collected from 3rd- and 5th-grade children will include: (1) observations of intake during school meals (breakfast and lunch);(2) measurement of PA using accelerometry during school hours;(3) recalls about diet and PA, diet only, or PA only;(4) social desirability;and (5) measurement of weight and height. Variables for dietary recall accuracy for food items are omission rate and intrusion rate, and for energy and macronutrients (protein, carbohydrate, fat) are correspondence rate and inflation ratio. Variables for PA recall accuracy are intensity-weighted total PA, intensity-weighted moderate-to-vigorous PA, total PA, moderate-to-vigorous PA, and vigorous PA. There are 4 research questions: 1) To what extent does children's recall accuracy depend on interview content (diet and PA;diet only;PA only)? 2) To what extent does children's recall accuracy depend on grade (3rd;5th)? 3) To what extent does children's recall accuracy depend on retention interval (about the same school day in an afternoon interview;about the previous school day in a morning interview)? 4) To what extent do children's BMI percentile and social desirability contribute to variability in recall accuracy? Our methodological project is timely and innovative due to the childhood obesity epidemic and need to assess both diet and PA. Our results will fill knowledge gaps with empirical evidence applicable to future school-based obesity prevention studies. PUBLIC HEALTH RELEVANCE: Investigators need a validated interview protocol that focuses on both sides of the energy balance equation to address the obesity epidemic in children. An integrated recall for both dietary intake and physical activity could enhance children's ability to accurately report this information because it could facilitate reporting of correct episodic memories rather than semantic (general) memory of the eating and physical activity events. Our results will fill several knowledge gaps with empirical evidence and provide a time-efficient approach for future school-based obesity prevention and health promotion studies that rely on children to self-report dietary intake and physical activity that occur at school (where parents are not present).